Spindle With Injector Duct And Piecing Method For An Airjet Spinning Machine

ABSTRACT

A spindle ( 10 ) for an airjet spinning machine is proposed, which, for guiding back (B) the yarn end after an interruption in a spinning process, contains: 
     an injector duct ( 1 ) which issues in the immediate vicinity of the spindle orifice ( 8 ). For guiding back, compressed air is admitted through the injector duct ( 1 ) and generates a suction action at the spindle end ( 11 ). After the yarn end has been guided back (B) level with the entrance of the injector duct ( 1 ) into the yarn guide duct ( 5 ), the yarn end is blown out of the spindle orifice ( 8 ) by the compressed air.

The present invention relates to a spindle for an airjet spinning machine according to the preamble of patent claim 1 and to a method for piecing after an interruption in a spinning process according to the preamble of patent claim 11.

The present invention relates to the field of airjet spinning machines. Airjet spinning machines have a multiplicity of spinning stations. In each spinning station, a yarn is spun from a longitudinal fiber structure which is supplied. In this case, the longitudinal fiber structure is first refined, that is to say the fiber quantity per unit length is reduced by drafting. The refined fiber composite is then spun into a yarn by a twist being imparted.

Yarn breaks, of course, cannot be prevented and result in a production interruption for the respective spinning station. The resumption of spinning takes place such that the free yarn end which has occurred due to the interruption is drawn out opposite to the spinning direction, called “upstream” in the jargon, beyond the twist-imparting point and is positioned. The initial region of the fiber composite, overlapping with the free yarn end, is subsequently connected to the latter in a known way in the spinneret by twist being imparted, and the spinning operation is thus resumed.

The thread take-off duct, also called a yarn duct or spindle duct, must have specific dimensions for spinning and structural reasons:

Length L:

-   -   L≈60-80 mm

Diameter d_(E) of the entry orifice of the thread take-off duct:

-   -   d_(E)≈0.8-1.2 mm

Diameter d_(A) of the exit orifice of the thread take-off duct:

-   -   d_(A)<2.0 mm; but d_(A)>d_(E)

The operation of guiding the yarn end back is very awkward because of the abovementioned dimensions of the spindle duct, to be precise a thin and long bore.

A method and a device for repiecing are known, in which, for the reintroduction of the yarn, an ejector duct is provided, through which compressed air is injected. This results in an injection air stream acting “upstream”. A spinning device is also disclosed, in which an injector duct is likewise provided, in which, by the admission of compressed air, the thread take-off duct can be moved away in order to make it easier to reintroduce the yarn. However, the arrangement of these injector ducts has not yet led to fully satisfactory results.

The object on which the present invention is based, therefore, is to specify, for a spinning station of an airjet spinning machine, a method and a spindle for carrying out the method, which, after an interruption in a spinning process, allow the yarn to be guided back reliably and accurately so as to produce a piecer, while the spindle is to have a simple configuration in structural terms.

This object is achieved, according to the invention, by means of the spindle specified in claim 1 and by means of the method specified in patent claim 11.

Advantageous embodiments of the present invention are specified in the dependent claims.

Owing to the arrangement according to the invention of an injector duct which issues directly at the spindle orifice, what is achieved, during piecing, by the supply of compressed air in the injector duct is that:

-   -   i) a suction action arises at the end of the yarn guide duct,         with the result that it becomes substantially easier to guide         the yarn end back,     -   ii) after the yarn end has come level with the injector duct, it         is blown out through the spindle orifice by the compressed air.

A spindle for an airjet spinning machine is thereby provided, by means of which the piecing after a yarn break is improved substantially, said spindle being capable of being produced in a simple way.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing in which:

FIG. 1 shows a basic illustration of a spindle with an arrangement according to the invention of an injector duct;

FIG. 1 a shows a view of a detail of a preferred arrangement of an injector duct;

FIG. 2 shows a structural configuration of a spindle with an injector duct according to the present invention.

FIG. 1 shows a basic illustration, not true to proportion, of a rotationally symmetrical spindle 10 with a yarn take-off duct 5. S designates the spinning direction in a normal spinning operation and B designates the guiding-back direction of the spun yarn to eliminate the thread break. On the exit side of the spindle 10, a spindle socket 2 with a conical orifice at an angle a is arranged. In order to make it easier to guide back the spun yarn, in spindle 10 an injector duct 1 is provided, the orifice of which is arranged near the spindle aperture 8, looking into the yarn duct 5. A groove 9 is lathe-turned out for the supply of compressed air. The diameter d₁ of the cylindrically designed injector duct 1 is in the following value range:

-   -   0.5 mm<d₁<0.7 mm; preferably 0.6 mm.

For the distance D between the spindle aperture and the entrance of the injector duct, the following value applies:

-   -   D<8 mm.

FIG. 1 a shows a preferred embodiment of the arrangement of the injector duct 1. The axis 7.1 of the injector duct 1 and the axis 7.2 of the yarn duct 5 intersect approximately at the spindle aperture 8. The angle of inclination β of the two abovementioned axes is preferably in a range of 5°-20°. In this preferred embodiment with the intersection of the two axes, the following optimal values are obtained for the distance D:

-   -   D<5 mm, preferably in the range 2 mm-3 mm.

The relation between the abovementioned distance D and the length L of the spindle is:

-   -   D<<L, where D<8 mm, particularly preferably D<5 mm.

FIG. 2 shows a preferred structural embodiment of the spindle 10 with the arrangement according to the invention of an injector duct 1:

The spindle 10 is formed by two parts 10.1, also called a spindle tip 10.1, and 10.2, also called a spinning tube 10.2, which are connected via a fit 6. The injector duct 1 has two parts 1.1 and 1.2 which are inclined axially with respect to one another and which differ from one another in their diameters d₁ and d₂:

-   -   d₂>d₁ and     -   d₂≈1.5 mm±0.5 mm.

The different dimensioning is due to manufacturing requirements: as a result, the spindle tube 10.2 with the larger diameter d₂ can be machined more simply and therefore produced more cost-effectively. Furthermore, both injector ducts 1.1 and 1.2 can be produced relatively simply as bores 1.1 and 1.2 from the parting plane F.

The diameter d_(E) of the entry orifice and the inside diameter d₁ are preferably in the following ratio: $0.3 < \frac{d_{1}}{d_{E}} < {0.8.}$

The two parts 10.1 and 10.2 are preferably adhesively bonded to one another for connection. So as not to have to arrange the axes of the two parts 1.1 and 1.2 of the injector duct exactly in alignment, in a preferred version the part 10.1 and/or the spindle tip has an annular gap 12 in the region of connection to the spindle tube 10.2.

Additionally or alternatively to the abovementioned dimensioning, there may be provision for the yarn duct 5 to have a conical shape 4 within the part 10.1. The conical shape 4 is determined by the cone length K and the diameters d_(A) and d_(E). K has a typical value of approximately 20 mm±7 mm.

The piecing method involves: the yarn end of the yarn is initiated in reverse by means of a corresponding actuation of the supply of compressed air into the groove 9. According to Bernoulli's law, a vacuum or a suction action arises at the spinning socket 2, so that the yarn end can move through the yarn duct 5 beyond the spindle aperture 8. The compressed air admitted into the injector duct 1 or 1.1/1.2 has the effect, when it emerges from the injector duct 1.1, that the yarn end guided back as a result of the suction action is blown out of the spindle aperture 8 and the guiding back of the yarn end is thus assisted.

The teaching according to the invention may be implemented by means of a free combination of the structural configurations and dimensionings explained above in FIGS. 1, la and 2, thus, for example, the diameters of the injector ducts 1.1 and 1.2 are largely independent of the configuration of the cone of the thread take-off duct 5 or of the cone of the spindle socket 2. 

1. A spindle (10) for a spinning station of an airjet spinning machine, which spindle (10) contains: a yarn guide duct (5) commencing with a spindle aperture (8), characterized in that an injector duct (1) issuing directly into the vicinity of the spindle aperture (8) is provided, through which compressed air is admitted during a guiding back of a yarn end, so that, upon the inlet of compressed air, a suction action arises at the end (11) of the yarn guide duct (5).
 2. The spindle (10) as claimed in claim 1, characterized in that the injector duct (1) is at a distance D from the spindle aperture (8) in a value range of D<8 mm.
 3. The spindle (10) as claimed in claim 1 or 2, characterized in that the injector duct (1) has an axis (7.1) and is inclined to the axis (7.2) of the spindle at an angle β with a value range of 5°<β<20°.
 4. The spindle (10) as claimed in one of claims 1 to 3, characterized in that the injector duct (1) has an axis (7.1) which essentially intersects with the axis (7.2) of the yarn take-off duct (5) in the spindle aperture (8).
 5. The spindle as claimed in one of claims 1 to 4, characterized in that the yarn take-off duct (5) has a conical shape (4) downstream of the aperture of the injector duct (1) in the spinning direction (S).
 6. The spindle (10) as claimed in one of claims 1 to 5, characterized in that the spindle (10) is designed in two parts in the form of a spinning tip (10.1) containing the spindle aperture (8) and a spinning tube (10), and the injector duct (1.1, 1.2) is contained in both parts (10.1, 10.2).
 7. The spindle (10) as claimed in claim 6, characterized in that the injector duct (1.1) has a smaller diameter d₁ in the spinning tip (10.1) than the diameter d₂ of the injector duct (1.2) in the spinning tube (10.2).
 8. The spindle (10) as claimed in claim 7, characterized in that the diameter d₂ has the following value range: d₂=1.5 mm±0.5 mm.
 9. The spindle (10) as claimed in one of claims 7 and 8, characterized in that the spindle tip (10.1) has an annular gap (12) in the region of connection to the spinning tube (10.2), so that the injector ducts (1.1, 1.2) contained in the two parts (10.1, 10.2) do not have to be arranged in alignment.
 10. The spindle (10) as claimed in one of claims 7 to 9, characterized in that the thread take-off duct (5) has an entry aperture (8) with a diameter d_(E), the ratio of the diameter d₁ of the injector duct (1.1) in the spinning tip (10.1) to the diameter d_(E) lying in the following value range: $0.3 < \frac{d_{1}}{d_{E}} < {0.8.}$
 11. A method for piecing after an interruption in a spinning process in a spindle (10), containing a yarn duct (5), of an airjet spinning machine, in which a yarn end and a fiber composite initial region are joined together, the yarn end being guided in reverse (B) through a spindle aperture (8) after the interruption in the spinning process has occurred, characterized in that an injector duct (1) issuing directly into the vicinity of the spindle aperture (8) is provided, through which compressed air is admitted during a guiding back of the yarn end, so that, upon the inlet of compressed air, a suction action arises at the end (11) of the yarn guide duct (5).
 12. The method as claimed in claim 11, characterized in that the yarn end is blown out through the spindle aperture (8) by means of the compressed air admitted into the injector duct (1). 